Display controller architecture for portable computers

ABSTRACT

A dual display mode portable computer is disclosed. The portable computer includes a flat-panel display, and a display controller for outputting an internal video signal to the flat panel display. The portable computer further includes means for receiving an external video signal, and a multiplexer for outputting the internal video signal to the flat-panel display during a first display mode, and for outputting the external video signal to the flat-panel display during a second display mode, thereby enabling the portable computer to act as a display device for an external computer.

FIELD OF THE INVENTION

The present invention relates to portable computers, and moreparticularly to a display controller architecture for portablecomputers.

BACKGROUND OF THE INVENTION

Laptops and notebooks are names for portable computers that have a flatscreen and usually weigh less than eight pounds. Most portable computershave connectors for an external monitor and keyboard for transformingthem into desktop computers.

FIG. 1 is a block diagram illustrating current display technology foundin portable computers. Like most computer systems, a portable computer10 includes internal hardware and software 12 for operating the system,and a display controller 14 for outputting an internal video signal 16to a flat panel display 18. The portable computer 10 also includes adigital-to-analog converter 20 and an external CRT connector 22 foroutputting the video signal 16 to an external monitor, such as a cathoderay tube (CRT) (not shown). With this type of display architecture, theportable computer 10 is capable of outputting its video signal on theflat-panel display 18, on the external CRT, or on both the flat-paneldisplay 18 and the external CRT at the same time.

The flat-panel display 18 tends to be one of the most expensivecomponents of the portable computer 10. Yet, today many portables 10become obsolete because various components, such as the processor,deliver lackluster performance relative to new computer systems.Therefore, it would be desirable to continue using the flat-paneldisplay 18 even after that portable computer 10 has become obsolete,perhaps as the monitor of a desktop PC (assuming the desktop PC has adual display adapter card). The problem is that today's portablecomputers 10 can only output video signals, but cannot receive videosignals from an external source for display on the flat-panel 18.

Accordingly, what is needed is a display controller architecture forportable computers that allows portable computers to display externalvideo signals. The present invention addresses such a need.

SUMMARY OF INVENTION

The present invention provides a dual display mode portable computer.The portable computer includes a flat-panel display, and a displaycontroller for outputting an internal video signal to the flat paneldisplay. The portable computer further includes means for receiving anexternal video signal, and a multiplexer for outputting the internalvideo signal to the flat-panel display during a first display mode, andfor outputting the external video signal to the flat-panel displayduring a second display mode, thereby enabling the portable computer toact as a display device for an external computer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating current display technology foundin portable computers.

FIG. 2 is a block diagram illustrating the display controllerarchitecture in accordance with one embodiment of the present invention.

FIG. 3 is a block diagram illustrating a display controller architecturein accordance with a second preferred embodiment of the presentinvention.

DETAILED DESCRIPTION

The present invention relates to display controller architecture forportable computers. The following description is presented to enable oneof ordinary skill in the art to make and use the invention and isprovided in the context of a patent application and its requirements.Various modifications to the preferred embodiments and the genericprinciples and features described herein will be readily apparent tothose skilled in the art. Thus, the present invention is not intended tobe limited to the embodiments shown but is to be accorded the widestscope consistent with the principles and features described herein.

The present invention provides a display architecture for portablecomputers that allows portable computers to receive and display theoutput of a desktop PC or another portable computer.

FIG. 2 is a block diagram illustrating the display controllerarchitecture in accordance with one embodiment of the present invention,where like components from FIG. 1 have like reference numerals.According to the present invention, the portable computer 30 is providedwith an extended mode display (XMD) that enables the portable computer30 to operate dual display modes. In normal display mode, the portalcomputer 30 displays the internal video signal 16 on the flat-paneldisplay 18, while in XMD mode, the portable computer 30 receives anddisplays an external video signal 32 on the flat-panel display 18.

In the first embodiment of the present invention, the display controllerarchitecture includes a dual mode display connector 34, a sensor 36, ananalog-to-digital (A/D) converter 38, converter logic 40, and amultiplexer 42. In a preferred embodiment, the dual mode displayconnector 34 is a 15-pin RGB connector for coupling a video cable froman external PC or portable to the portable computer 30. The externalvideo signal 32 preferably comprises RGB analog input and timingsignals.

When the external video signal 32 is received on the connector 34, theA/D converter 38 converts the signal 32 into a digital signal. Theconverter logic 40 then maps the output of the A/D converter 38 into aformat required by the flat panel display 18. After the conversion, theformatted digital video signal is input into the multiplexer 42. Themultiplexer 42 has two inputs: the standard internal video signal 16from the display controller 14, and the external video signal 32 outputfrom converter logic 40. The multiplexer 42 outputs either the internalvideo signal 16 or the external video signal 32 to the flat-paneldisplay 18 depending on the current display mode of the portablecomputer 30.

In a preferred embodiment, controls are added to the portable computerBIOS that would enable the portable computer 30 to operate in thefollowing modes:

-   -   1) normal display mode—flat-panel only,    -   2) normal display mode—flat-panel and an external CRT (same        image on both displays),    -   3) normal display mode—external CRT only, and    -   4) XMD mode—external signal displayed on external CRT and        flat-panel.

In a preferred embodiment of the present invention, the display modes ofthe portable computer can be controlled in a variety of ways includingautomatic detection or by an explicit user command. The automatic moderequires the sensor 36 to automatically detect an external devicecoupled to the dual mode display connector 34 and driving the externalvideo signal 32 through the connector 32 when the portable computer 30is powered-on. This can be an extension of the power-on sequence of theportable computer 30. Alternatively, if the portable computer 30 and theexternal computer are already powered-on and the two are connected, itis possible for both computers to detect each other. In this case, theuser may be given an option to select a “hot plug” mode. In any event,once the sensor 36 detects the external video signal 32, the portablecomputer 30 may be switched to XMD mode.

The second method for controlling the display modes of the portablecomputer 30 is through the use of a dual mode display software driver 34that enable the user to manually invoke the XMD mode either by clickingon an icon or by a key sequence. In a preferred embodiment, the dualmode display driver 34 displays a dialog box at startup that allows theuser to select automatic switching mode or manual switching mode. Thedriver may also give the user an option to select the resolution of theexternal computer (e.g., VGA, XVGA, or SVGA) when it cannotautomatically be detected.

The manual method for switching the display mode is preferable over theautomatic detection method because the user can toggle the displaybetween the primary flat-panel display 18 and the external PC. Morespecifically, the portable computer 30 remains on and fully booted evenwhen the flat-panel 18 is used as the second display device of theexternal PC, and a hot key sequence is used to toggle flat-panel display18.

Once the display mode of the portable computer 30 is set, a controlsignal 36 is sent to the multiplexer 42 to control which video signal issent to the flat-panel display 18. If the portable computer 30 is innormal display mode, then the multiplexer 14 outputs the internal videosignal 16 to the flat-panel display 18. If, however, the portablecomputer 30 is in the XMD mode, the multiplexer 42 outputs the externalvideo signal 32 to the flat-panel display 18. A primary advantage ofusing the multiplexer-based display architecture is that multiplexer 42eliminates the need for a custom graphics controller, and the displayarchitecture can be implemented into current portable computer designs.

Referring now to FIG. 3, a display controller architecture is shownaccording to a second preferred embodiment of the present invention,where like components from FIGS. 1 and 2 have like reference numerals.The second embodiment adds a dual mode display connector 52 to theexisting external CRT connector 22 of the portable computer 50 thatconnects to the external CRT connector 22, rather than adding a newconnector to the portable computer. The CRT connector 22 is a femaletype connector. Therefore, the dual mode display connector 52 is afemale to male type connector for accepting a display cord from anothercomputer. The advantage of using the dual mode display connector 52 isthat current portable computers do not have to be redesigned to accept anew input connector.

According to the second embodiment, a second multiplexer 54 is connectedbetween the external CRT connector 22 and the D/A converter 20. Innormal display mode, the D/A converter 20 outputs the internal videosignal that drives an external CRT to the external CRT connector 22. InXMD mode, a control signal 56 is sent to the second multiplexer 54 toisolate the D/A converter 20 and to allow the external video signal 32to enter the external CRT connector 22 through the dual mode displayconnector 52. The external video signal 32 is then input to the A/Dconverter 38 and converter logic 40, and output to the flat-paneldisplay 18 through the multiplexer 42, as described above.

A display architecture that provides portable computers with an extendedmode display has been described. The present invention has beendescribed in accordance with the embodiments shown, and one of ordinaryskill in the art will readily recognize that there could be variationsto the embodiments, and any variations would be within the spirit andscope of the present invention. Accordingly, many modifications may bemade by one of ordinary skill in the art without departing from thespirit and scope of the appended claims.

1. A portable computer comprising: a flat-panel display; a displaycontroller for outputting an internal video signal to the flat paneldisplay; means for receiving an external video signal; a multiplexer foroutputting either the internal video signal or the external video signalto the flat-panel display; and an analog-to-digital converter andconverter logic coupled between the receiving means and the multiplexerfor converting the external video signal into a format required by theflat-panel display.
 2. The portable computer of claim 1 wherein thereceiving means includes a sensor for automatically sensing the externalvideo signal and causing the multiplexer to output the external videosignal for display.
 3. The portable computer of claim 2 whereinreceiving means includes a software driver that enables a user tomanually select between displaying the internal video signal or theexternal video signal.
 4. The portable computer of claim 3 wherein thereceiving means includes a dual mode display connector coupled to theanalog-to-digital converter for receiving the external video signal. 5.The portable computer of claim 3 wherein the portable computer includesan external CRT connector and wherein the receiving means includes adual mode display adapter coupled to the external CRT connector foraccepting the external video signal.
 6. The portable computer of claim 5wherein the portable computer further includes a second multiplexercoupled between the external CRT connector and adigital-analog-converter for isolating the output of thedigital-analog-converter so that the external video signal may bereceived through the dual mode display adapter and the external CRTconnector.
 7. A method for enabling a portable computer to display anexternal video signal, the portable computer having a flat-paneldisplay, the method comprising the steps of: (a) providing the portablecomputer with means for receiving the external video signal; (b)inputting an internal video signal to a multiplexer; (c) inputting theexternal video signal to the multiplexer; (d) providing the portablecomputers with dual display modes, such that in a first display mode,the multiplexer outputs the internal video signal to the flat-paneldisplay, while in a second display mode, the multiplexer outputs theexternal video signal to the flat-panel display, thereby enabling theportable computer to act as a display device for an external computer;and (e) coupling an analog-to-digital converter and converter logicbetween the receiving means and the multiplexer for converting theexternal video signal into a format required by the flat-panel display.8. The method of claim 7 wherein step (a) further includes the step of:providing the receiving means with a sensor for automatically sensingthe external video signal and causing the multiplexer to output theexternal video signal for display.
 9. The method of claim 8 wherein step(a) further includes the step of: providing the receiving means with asoftware driver enables a user to manually select between displaying theinternal video signal or the external video signal.
 10. The method ofclaim 9 wherein step (a) further includes the step of: coupling a dualmode display connector to the analog-to-digital converter for receivingthe external video signal.
 11. The method of claim 9 wherein theportable computer includes an external CRT connector and wherein step(a) further includes the step of: coupling a dual mode display adapterto the external CRT for accepting the external video signal.
 12. Themethod of claim 11 wherein step (a) further includes the step of:coupling a second multiplexer between the external CRT connector and adigital-analog-converter for isolating the output of thedigital-analog-converter so that the external video signal may bereceived through the dual mode display adapter and the external CRTconnector.